Preparation of 2-amino-thiazole



; Patented Oct. 16,

- UNITED sures PATENT orn-ctr:

PREPARATION OF Z-AMINO-THIAZQLE Edgar C. Brltton and Kenneth G. Harding, Midland, Mich, asslgnors to The Dow Chemical Company, Mldland,-'Mich., a corporation of No Drawing. Application owner 23, ms.

Serial No. 501,416

scarin -(01.261402) a This invention concer'ns'an improved method for the preparation oi 2-amino-thiazole.

The compound, 2 -amino-thiazole, has heretoiore been prepared by reacting ethyl alpha-beta-dichloro-ethyl ether with an aqueous solution of thiourea in accordance with the equation:

H -mmoinionnnci its indicated by this equation, the dichloro-diethyl ether and the 'thiourea react together to form 2-amino-thiazole and an equimolecular amount of ethyl alcohol. The latter is obtained in aqueoussolution and usually. in amount such as not to warrant the extra steps which would Accordbe required for recovery the same. 8 57. the formation or ethyl alcohol represents.

a loss of a portion of the ether reactant. 9

We have found that such loss'may be avoided by employing, in place of anethyl alpha-betadichloro-ethyl ether, a bis-(alpha-beta-dihaloethyl) ether as a reactant. when such bis-(dihalo-ethyl) ether is used, both halves of the reaction. Accordingly, a considerable saving is effected by employing the bis-dihalo-ethyl ether. in place of an ethyl dihalo-ethyl ether, as a reactant. It may be mentioned that the bis-dihalo-ethyl ether is readily prepared by the reaction of a halogen, e. s. chlorine or bromine, with divinyl ether. When using the bis-(dlhaloethyl) ether was. reactant, the reaction occurs in accordance with the equation:

v It should be mentioned that, although water is among the products formed by the reaction, the

. presence of water in the starting materials is necessary in order to initiate the reaction.

Except for the substitution of the bis-dihalo- 'ethyl ether in place of the ethyl dihalo-ethyl .ether heretofore employed, the reaction may be carried out as usual. For instance, a bis-dihalo-ethyl ether may be added to an aqueous thiourea solution and the mixture be heated to a reaction temperature, e. g.- of 90 C. or above,

until the reaction is substantially complete. e Usually the ether and thiourea reactants are 5 be ut 38.5 arm.

ether molecule enter into the reaction and two molecular equivalents of 2-amino-thiazole are i formed per mole of said ether consumed inthe employed in approximately equimolecular proportions, but either reactant may be used in considerable excess 1; desired. The reaction mixture is usually heated to boiling under reflux at at- -mospheric pressure, but the reaction may. be

carried out in a corrosion-resistant bomb .or' autoclave at higher temperatures, e. g. 1509 C.

or higher. The reaction is substantially complete when the bis-dihalo-ethyl-ether phase or the reaction mixture has been consumed and is no longer observable. productis recovered by conventional procedure.

The following examples illustrate certain ways in which the principle of the invention has been employed, but are not to be construed as iimitins the invention: 1

- Eeample 1 e A mixture of 19 grams (0.25 mole) oi thiourea,

49 Brains (0.125 mole) of bis-(alpha-beta-dibromo-ethyl) ether and 100 cc. oi water was heated to boiling under reflux for 3 hours, at theend of which time the ether layer of the mixture had disappeared, indicating that the reaction was substantially complete. The mix ture was cooled to about room temperature,

filtered, and rendered slightly alkaline by treat ment with an aqueous sodium hydroxide solutron. It was then decolorized by treatment with activated charcoal, and the latter was removed by filtration; The vZ-aminu-thiazole product was extracted from. the flltrate with diethyl ether and was recovered from the extract by distilling oii the ether. There was obtained 27 grams oi somewhatimpure 2-amino-thiazole. The product was recrystallized from ethyl alcohol where by there was obtained 21.6 grams (0.216 mole), i. e. 86 per cent 01 the theoretical yield, 01 sub stantially pure Z-amino-thiazole.

Example -2 I A mixture oi'207'grams of bis- (alpha-beta-dichloro-ethyl) ether 01 about per cent purity,

arms at thiourea and 700 cc. of water was boiled under reflux for 16 hours. A 260 gram' portion of the reaction mixture was evaporated under vacuum, 1. e. at about 40 millimeters absolute pressure, to obtain a concentrated residual mixture weighing 68 grams. The 2-amlno-thl azole product was extracted from the residue with ether, after which ether was evaporated from the extract. There remained 41.5 grams of somewhat impure 2-amino' thiazole. The theoretical yield of pure 2-amino-thiazole from the 260 gram portion of the reaction liquor would The z-amino-thiazole water.

Othei-modes of applying the principle of the invention may be employed instead of those explained, chance bein: made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps .be em- Played.

We therefore particularly =p0int out and dis- 7 tinctly claim as our invention:

1. In a. method of making 2-ami o-thiezole, the step ot reectin: a. bis-(elpha-beto-dihfloethylletherwith thioureein' the presence of water.

. 2. In a' method of making 2-amino-thiezole.

the step of reacting bis-(elpha-beta-dibmm0-' ethvl) ether with thiourea in the presence of water. V

3. In a method of making 2-amino-thiazole. the step of reacting bis-(alpha-beta-dichlomethyl) ether with thiourea in the presence of mm c. amen. mums a. ammo. 

